Inducible offences affect predator–prey interactions and life‐history plasticity in both predators and prey

Abstract

1. Phenotypic plasticity can have strong impacts on predator-prey interactions. Although much work has examined the effects of inducible defences, less understood is how inducible offences in predators affect predator-prey interactions and predator and prey phenotypes. 2. Here, we examine the impacts of an inducible offence on the interactions and life histories of a cohort of predatory Hynobius retardatus salamander larvae and their prey, Rana pirica tadpoles. We examined larval (duration, survival) and post-metamorphic (size) traits of both species after manipulating the presence/absence of tadpoles and salamanders with offensive (broadened gape width) or non-offensive phenotypes in pond enclosures. 3. Offensive phenotype salamanders reduced tadpole survival and metamorph emergence by 58% compared to tadpole-only treatments, and by over 30% compared to non-offensive phenotypes. Average time to metamorphosis of frogs was delayed by 30% in the presence of sal-amanders, although this was independent of salamander phenotype. Thus, offensive phenotype salamanders reduced the number of tadpoles remaining in the pond over time by reducing tadpole survival, not by altering patterns of metamorph emergence. Offensive phenotypes also caused tadpoles to metamorphose 19% larger than no salamander treatments and 6% larger than non-offensive phenotype treatments. Pooled across salamander treatments , tadpoles caused salamanders to reach metamorphosis faster and larger. Moreover, in the presence of tadpoles, offensive phenotype salamanders metamorphosed 25% faster and 5% larger than non-offensive phenotype salamanders, but in their absence, neither their size nor larval period differed from non-offensive phenotype individuals. 4. To our knowledge, this study is the first to demonstrate that inducible offences in predators can have strong impacts on predator and prey phenotypes across multiple life stages. Since early metamorphosis at a larger size has potential fitness advantages, the impacts of offensive phenotypes on frog and salamander life histories likely have significant consequences for individuals and populations. Furthermore, increased predation on tadpoles likely causes offensive phenotype individuals to have strong impacts on pond communities. Future studies should examine the fitness consequences of morphological and life-history plasticity across multiple life stages and should address the population and community level consequences of offensive phenotypes.

Habitat‐mediated carry‐over effects lead to context‐dependent outcomes of species interactions

“…Trait variation in response to present environmental cues (e.g. development of anti-predator morphologies or nutrient stress) frequently affects interactions between diverse taxa such as plants and herbivores (terHorst & Lau 2012), protists (DeLong, Hanley & Vasseur 2013), invertebrates (Hoverman & Relyea 2009) and vertebrates (Kishida et al 2013). However, trait variation coming from previous habitats is typically neglected in spatial models of competitive coexistence (HilleRisLambers et al 2012).…”

Predator cannibalism can intensify negative impacts on heterospecific prey

“…Although past studies have evaluated the effects of cannibalism on the abundance of heterospecific prey , Rudolf 2006, Law and Rosenheim 2011, they did not examine how cannibalism affects the phenotypic characteristics of the two populations. We expect that, by exploring the consequences of cannibalism on the phenotypic characteristics of predator and prey populations, we will gain insight into the ecological consequences of cannibalism, because phenotypic traits such as behavior, life history, and morphology of key species influence both ecological interactions and trait evolution in a community (Agrawal 2001, Werner and Peacor 2003, Miner et al 2005, Takatsu and Kishida 2013, Kishida et al 2014.…”

Feedback between size balance and consumption strongly affects the consequences of hatching phenology in size‐dependent predator–prey interactions

“…A). Since salamander larvae with the offensive morph consume more frog tadpoles than those with the non‐offensive morph even if their canonical size (body size) is similar (Takatsu and Kishida , Kishida et al ), we can infer that the allometric growth due to the inducible offence itself contributed to the predation success of the early‐hatched salamander larvae in this experiment, independently of ordinary growth. Inducible offences are widespread among predator taxa (reviewed by Kishida et al ) and theory suggests that the evolution of inducible offences is part of an adaptive phenotypic plasticity strategy of predators to overcome the inducible defences of their prey (Mougi et al ).…”

“…Diff erential eff ects on life-history traits among the treatments could refl ect diff erences in predation pressure among them. Th e results of a recent fi eld study (Kishida et al 2014), in which the presence or absence of off ensive and non-off ensive morphs of salamander larvae were experimentally manipulated, support this possibility. Kishida et al (2014) showed that the frog tadpoles were larger at metamorphosis and they metamorphosed later when they were exposed to stronger predation pressures from off ensivemorph salamander larvae.…”